Control of unsaturation in polymers produced in solution process

ABSTRACT

The copolymerization of ethylene with an optional comonomer is conducted in the presence of a catalyst having a specific aryloxy ether ligand structure. The process enables very high conversions of ethylene to polyethylene at very short residence times when conducted under conditions of pressures of at least 10.3 MPa and high ethylene feed concentrations of from 70 to 150 grams per liter. Using these polymerization conditions, the level of unsaturation may be controlled by the polymerization temperature: for example, a level of 0.09 vinyl groups per 1000 carbon atoms was observed at a polymerization temperature of 160° C. and a level of 0.22 vinyls per 1000 carbon atoms was observed at 220° C.

The polymerization of ethylene under solution conditions is a well knownart in which ethylene and an optional comonomer are contacted in thepresence of catalyst in a solvent for the monomer(s) and the resultingpolymer. It will be recognized by those skilled in the art that it isdesirable to conduct solution polymerizations at elevated temperaturesbecause this reduces the viscosity of the polymer solution (which canenable higher polymer concentrations) and because the higherpolymerization temperature reduces the amount of energy that is need torecover the polymer from the solution. It will also be recognized thatit is difficult to operate at high temperatures because most of thecommon coordination catalysts quickly deactivate at temperatures inexcess of 150° C.

The productivity of a solution polymerization process is also influencedby the reaction time (or “Hold Up Time”) that is required to achieve atarget rate of ethylene conversion (i.e. ethylene to polyethylene). Ashort residence time with high conversion provides high productivity. Wehave now discovered a highly productive process for the (co)polymerization of ethylene using a specified catalyst under conditionsof relatively high pressure and ethylene feed concentration.

We have now observed that highly productive ethylene polymerizations maybe conducted with catalysts having aryloxy ligands using comparativelyhigh ethylene feed concentrations and comparatively high pressures,thereby facilitation short reaction times. In addition, we havediscovered that the level of unsaturation in polymers produced by thisprocess may be controlled by changing the polymerization temperature.

In an embodiment, the present disclosure provides a catalyst systemincluding:

A) a catalyst defined by the formula:

M is titanium, zirconium, or hafnium, each independently being in aformal oxidation state of +4;n is 2;Each X independently is a monodentate ligand;X is chosen in such a way that the metal-ligand complex of formula (I)is, overall, neutral;L is hydrocarbylene or heterohydrocarbylene, wherein the hydrocarbylenehas a portion that includes a 1-carbon atom to 6-carbon atom linkerbackbone linking the O atoms in formula (I) and the heterohydrocarbylenehas a portion that includes a 1-atom to 6-atom linker backbone linkingthe O atoms in formula (I), wherein each atom of the 1-atom to 6-atomlinker backbone of the heterohydrocarbylene independently is a carbonatom or a heteroatom, wherein each heteroatom independently is O, S,S(O), S(O)₂, Si(R^(C))₂, Ge(R^(C))₂, P(R^(P)), or N(R^(N)), whereinindependently each R^(C) is unsubstituted (C1-C18)hydrocarbyl or the twoR^(C) are taken together to form a (C2-C19)alkylene, each R^(P) isunsubstituted (C1-C18)hydrocarbyl; and each R^(N) is unsubstituted(C1-C18)hydrocarbyl, a hydrogen atom or absent;Each of R^(1a), R^(1b), R^(2a), R^(2b), R^(3a), R^(3b), R^(4a), R^(4b),R^(5c), R^(5d), R^(6c), R^(6d), R^(7c), R^(7d), R^(8e), R^(8f), R^(9e),R^(9f), R^(10e), R^(10f), R^(11e), R^(11f), R^(12e), R^(12f), R^(13e),R^(13f), R^(14e), R^(14f), R^(15e), R^(15f) independently is a hydrogenatom; hydrocarbyl; heterohydrocarbyl; or halogen atom;

B) and an activator.

In some embodiments, L is hydrocarbylene and includes a 1-carbon atom to6-carbon atom linker. In some embodiments, M is hafnium.

In some embodiments, at least one C₃ to C₁₀ comonomer is chosen frompropylene; 1-butene; 1-hexene and 1-octene.

In some embodiments, said activator includes a boron ionic activator. Insome embodiments, said activator includes a boron ionic activator and analumoxane. In some embodiments, the mole ratio of boron contained insaid boron ionic activator to the hafnium contained in said catalyst isfrom 1:1 to 2:1 and the mole ratio of aluminum contained in saidalumoxane to the hafnium contained in said catalyst is from 2:1 to1000:1.

In an embodiment, the present disclosure provides a process for the(co)polymerization of ethylene and, optionally, at least one alphaolefin comonomer wherein said process is conducted under solutionpolymerization conditions using a catalyst system including:

A) a catalyst defined by the formula:

M is titanium, zirconium, or hafnium, each independently being in aformal oxidation state of +2, +3, or +4;n is an integer of from 0 to 3, wherein when n is 0, X is absent;Each X independently is a monodentate ligand that is neutral,monoanionic, or dianionic; or two X are taken together to form abidentate ligand that is neutral, monoanionic, or dianionic;X and n are chosen in such a way that the metal-ligand complex offormula (I) is, overall, neutral;L is hydrocarbylene or heterohydrocarbylene, wherein the hydrocarbylenehas a portion that includes a 1-carbon atom to 6-carbon atom linkerbackbone linking the O atoms in formula (I) and the heterohydrocarbylenehas a portion that includes a 1-atom to 6-atom linker backbone linkingthe O atoms in formula (I), wherein each atom of the 1-atom to 6-atomlinker backbone of the heterohydrocarbylene independently is a carbonatom or a heteroatom, wherein each heteroatom independently is O, S,S(O), S(O)₂, Si(R^(C))₂, Ge(R^(C))₂, P(R^(P)), or N(R^(N)), whereinindependently each R^(C) is unsubstituted (C1-C18)hydrocarbyl or the twoR^(C) are taken together to form a (C2-C19)alkylene, each R^(P) isunsubstituted (C1-C18)hydrocarbyl; and each R^(N) is unsubstituted(C1-C18)hydrocarbyl, a hydrogen atom or absent;Each of R^(1a), R^(1b), R^(2a), R^(2b), R^(3a), R^(3b), R^(4a), R^(4b),R^(5c), R^(5d), R^(6c), R^(6d), R^(7c), R^(7d), R^(8e), R^(8f), R^(9e),R^(9f), R^(10e), R^(10f), R^(11e), R^(11f), R^(12e), R^(12f), R^(13e),R^(13f), R^(14e), R^(14f), R^(15e), R^(15f) independently is a hydrogenatom; hydrocarbyl; heterohydrocarbyl; or halogen atom;

B) and an activator, wherein said solution polymerization is conductedunder the following conditions:

1) an ethylene feed concentration of from 70 to 150 grams per liter ofsolvent;

2) a pressure of from 10.3 to 31 MPa; and

3) a reactor residence time of from 0.5 to 5 minutes, with the provisothat from 50 to 95 weight % of the ethylene in said feed is polymerizedwithin said residence time of from 0.5 to 5 minutes, with the provisothat the polymerization is conducted at a temperature of greater than160° C. so as to produce an ethylene polymer having a degree ofunsaturation of greater than 0.1 vinyl groups per 1000 carbon atoms asmeasured by Fourier Transform Infra Red spectroscopy.

Other than in the examples or where otherwise indicated, all numbers orexpressions referring to quantities of ingredients, extrusionconditions, etc., used in the specification and claims are to beunderstood as modified in all instances by the term ‘about’.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the desired properties thatthe various embodiments desire to obtain. At the very least, and not asan attempt to limit the application of the doctrine of equivalents tothe scope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. The numerical values set forth inthe specific examples are reported as precisely as possible. Anynumerical values, however, inherently contain certain errors necessarilyresulting from the standard deviation found in their respective testingmeasurements.

It should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10; that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations.

All compositional ranges expressed herein are limited in total to and donot exceed 100 percent (volume percent or weight percent) in practice.Where multiple components can be present in a composition, the sum ofthe maximum amounts of each component can exceed 100 percent, with theunderstanding that, and as those skilled in the art readily understand,that the amounts of the components actually used will conform to themaximum of 100 percent.

In order to form a more complete understanding of this disclosure thefollowing terms are defined and should be used with the accompanyingfigures and the description of the various embodiments throughout.

As used herein, the terms “monomer” “comonomer” refer to a smallmolecule that may chemically react and become chemically bonded withitself or other monomers to form a polymer.

As used herein, the term “α-olefin” is used to describe a monomer havinga linear hydrocarbon chain containing from 3 to 20 carbon atoms having adouble bond at one end of the chain; an equivalent term is “linearα-olefin”.

As used herein, the terms “ethylene polymer” and “polyethylene”, referto macromolecules produced from ethylene and optionally one or moreadditional monomers; regardless of the specific catalyst or specificprocess used to make the ethylene polymer. In the polyethylene art, theone or more additional monomers are frequently called “comonomer(s)” andoften include α-olefins. The term “homopolymer” refers to a polymer thatcontains only one type of monomer. Common ethylene polymers include highdensity polyethylene (HDPE), medium density polyethylene (MDPE), linearlow density polyethylene (LLDPE), very low density polyethylene (VLDPE),ultralow density polyethylene (ULDPE), plastomer and elastomers.

The term “thermoplastic” refers to a polymer that becomes liquid whenheated, will flow under pressure and solidify when cooled. Thermoplasticpolymers include ethylene polymers as well as other polymers used in theplastic industry; non-limiting examples of other polymers commonly usedin film applications include barrier resins (EVOH), tie resins,polyethylene terephthalate (PET), polyamides and the like.

As used herein the term “monolayer film” refers to a film containing asingle layer of one or more thermoplastics.

As used herein, the terms “hydrocarbyl”, “hydrocarbyl radical” or“hydrocarbyl group” refers to linear, branched, or cyclic, aliphatic,olefinic, acetylenic and aryl (aromatic) radicals including hydrogen andcarbon that are deficient by one hydrogen.

As used herein, an “alkyl radical” includes linear, branched and cyclicparaffin radicals that are deficient by one hydrogen radical;non-limiting examples include methyl (—CH₃) and ethyl (—CH₂CH₃)radicals. The term “alkenyl radical” refers to linear, branched andcyclic hydrocarbons containing at least one carbon-carbon double bondthat is deficient by one hydrogen radical.

As used herein, the term “aryl” group includes phenyl, naphthyl, pyridyland other radicals whose molecules have an aromatic ring structure;non-limiting examples include naphthylene, phenanthrene and anthracene.An “arylalkyl” group is an alkyl group having an aryl group pendantthere from; non-limiting examples include benzyl, phenethyl andtolylmethyl; an “alkylaryl” is an aryl group having one or more alkylgroups pendant there from; non-limiting examples include tolyl, xylyl,mesityl and cumyl.

As used herein, the phrase “heteroatom” includes any atom other thancarbon and hydrogen that can be bound to carbon. A“heteroatom-containing group” is a hydrocarbon radical that contains aheteroatom and may contain one or more of the same or differentheteroatoms. In one embodiment, a heteroatom-containing group is ahydrocarbyl group containing from 1 to 3 atoms chosen from boron,aluminum, silicon, germanium, nitrogen, phosphorous, oxygen and sulfur.Non-limiting examples of heteroatom-containing groups include radicalsof imines, amines, oxides, phosphines, ethers, ketones, oxoazolinesheterocyclics, oxazolines, thioethers, and the like. The term“heterocyclic” refers to ring systems having a carbon backbone thatinclude from 1 to 3 atoms chosen from boron, aluminum, silicon,germanium, nitrogen, phosphorous, oxygen and sulfur.

As used herein the term “unsubstituted” means that hydrogen radicals arebounded to the molecular group that follows the term unsubstituted. Theterm “substituted” means that the group following this term possessesone or more moieties that have replaced one or more hydrogen radicals inany position within the group; non-limiting examples of moieties includehalogen radicals (F, Cl, Br), hydroxyl groups, carbonyl groups, carboxylgroups, amine groups, phosphine groups, alkoxy groups, phenyl groups,naphthyl groups, C₁ to C₁₀ alkyl groups, C₂ to C₁₀ alkenyl groups, andcombinations thereof. Non-limiting examples of substituted alkyls andaryls include: acyl radicals, alkylamino radicals, alkoxy radicals,aryloxy radicals, alkylthio radicals, dialkylamino radicals,alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyl radicals,alkyl- and dialkyl-carbamoyl radicals, acyloxy radicals, acylaminoradicals, arylamino radicals and combinations thereof.

As used herein, the term “oligomers” refers to an ethylene polymer oflow molecular weight, e.g., an ethylene polymer with a weight averagemolecular weight (Mw) of about 2000 to 3000 daltons. Other commonly usedterms for oligomers include “wax” or “grease”. As used herein, the term“light-end impurities” refers to chemical compounds with relatively lowboiling points that may be present in the various vessels and processstreams within a continuous solution polymerization process;non-limiting examples include, methane, ethane, propane, butane,nitrogen, CO₂, chloroethane, HCl, etc.

A. Catalyst

The catalyst is defined by the formula:

M is titanium, zirconium, or hafnium, each independently being in aformal oxidation state of +2, +3, or +4;n is an integer of from 0 to 3, wherein when n is 0, X is absent;Each X independently is a monodentate ligand that is neutral,monoanionic, or dianionic; or two X are taken together to form abidentate ligand that is neutral, monoanionic, or dianionic;X and n are chosen in such a way that the metal-ligand complex offormula (I) is, overall, neutral;L is hydrocarbylene or heterohydrocarbylene, wherein the hydrocarbylenehas a portion that includes a 1-carbon atom to 6-carbon atom linkerbackbone linking the O atoms in formula (I) and the heterohydrocarbylenehas a portion that includes a 1-atom to 6-atom linker backbone linkingthe O atoms in formula (I), wherein each atom of the 1-atom to 6-atomlinker backbone of the heterohydrocarbylene independently is a carbonatom or a heteroatom, wherein each heteroatom independently is O, S,S(O), S(O)₂, Si(R^(C))₂, Ge(R^(C))₂, P(R^(P)), or N(R^(N)), whereinindependently each R^(C) is unsubstituted (C1-C18)hydrocarbyl or the twoR^(C) are taken together to form a (C2-C19)alkylene, each R^(P) isunsubstituted (C1-C18)hydrocarbyl; and each R^(N) is unsubstituted(C1-C18)hydrocarbyl, a hydrogen atom or absent;Each of R^(1a), R^(1b), R^(2a), R^(2b), R^(3a), R^(3b), R^(4a), R^(4b),R^(5c), R^(5d), R^(6c), R^(6d), R^(7c), R^(7d), R^(8e), R^(8f), R^(9e),R^(9f), R^(10e), R^(10f), R^(11e), R^(11f), R^(12e), R^(12f), R^(13e),R^(13f), R^(14e), R^(14f), R^(15e), R^(15f) independently is a hydrogenatom; hydrocarbyl; heterohydrocarbyl; or halogen atom.

In an embodiment, the catalyst is defined by the formula:

M is titanium, zirconium, or hafnium, each independently being in aformal oxidation state of +4;n is 2;Each X independently is a monodentate ligand;X is chosen in such a way that the metal-ligand complex of formula (I)is, overall, neutral;L is hydrocarbylene or heterohydrocarbylene, wherein the hydrocarbylenehas a portion that includes a 1-carbon atom to 6-carbon atom linkerbackbone linking the O atoms in formula (I) and the heterohydrocarbylenehas a portion that includes a 1-atom to 6-atom linker backbone linkingthe O atoms in formula (I), wherein each atom of the 1-atom to 6-atomlinker backbone of the heterohydrocarbylene independently is a carbonatom or a heteroatom, wherein each heteroatom independently is O, S,S(O), S(O)₂, Si(R^(C))₂, Ge(R^(C))₂, P(R^(P)), or N(R^(N)), whereinindependently each R^(C) is unsubstituted (C1-C18)hydrocarbyl or the twoR^(C) are taken together to form a (C2-C19)alkylene, each R^(P) isunsubstituted (C1-C18)hydrocarbyl; and each R^(N) is unsubstituted(C1-C18)hydrocarbyl, a hydrogen atom or absent;Each of R^(1a), R^(1b), R^(2a), R^(2b), R^(3a), R^(3b), R^(4a), R^(4b),R^(5c), R^(5d), R^(6c), R^(6d), R^(7c), R^(7d), R^(8e), R^(8f), R^(9e),R^(9f), R^(10e), R^(10f), R^(11e), R^(11f), R^(12e), R^(12f), R^(13e),R^(13f), R^(14e), R^(14f), R^(15e), R^(15f) independently is a hydrogenatom; hydrocarbyl; heterohydrocarbyl; or halogen atom.

In an embodiment, L is hydrocarbylene and includes a 1-carbon atom to6-carbon atom linker.

In an embodiment, the catalyst is defined by the formula:

B. Cocatalyst (Also Known as “Activator”)

The catalyst is rendered catalytically active by contacting it to, orcombining it with, the activating co-catalyst or by using an activatingtechnique such as those that are known in the art for use withmetal-based olefin polymerization reactions. Suitable activatingco-catalysts for use herein include alkyl aluminums; polymeric oroligomeric alumoxanes (also known as aluminoxanes); neutral Lewis acids;and non-polymeric, non-coordinating, ion-forming compounds (includingthe use of such compounds under oxidizing conditions). A suitableactivating technique is bulk electrolysis. Combinations of one or moreof the foregoing activating co-catalysts and techniques are alsocontemplated. The term “alkyl aluminum” means a monoalkyl aluminumdihydride or monoalkylaluminum dihalide, a dialkyl aluminum hydride ordialkyl aluminum halide, or a trialkylaluminum. Aluminoxanes and theirpreparations are known at, for example, United States Patent (USP) U.S.Pat. No. 6,103,657. Examples of polymeric or oligomeric alumoxanes aremethylalumoxane, triisobutylaluminum-modified methylalumoxane, andisobutylalumoxane.

Exemplary Lewis acid activating co-catalysts are Group 13 metalcompounds containing from 1 to 3 hydrocarbyl substituents as describedherein. In some embodiments, exemplary Group 13 metal compounds aretri(hydrocarbyl)-substituted-aluminum or tri(hydrocarbyl)-boroncompounds. In some other embodiments, exemplary Group 13 metal compoundsare tri(hydrocarbyl)-substituted-aluminum or tri(hydrocarbyl)-boroncompounds are tri((C₁-C₁₀) alkyl)aluminum or tri((C₆-C₁₈)aryl)boroncompounds and halogenated (including perhalogenated) derivativesthereof. In some other embodiments, exemplary Group 13 metal compoundsare tris(fluoro-substituted phenyl)boranes, in other embodiments,tris(pentafluorophenyl)borane. In some embodiments, the activatingco-catalyst is a tris((C₁-C₂₀)hydrocarbyl) borate (e.g., trityltetrafluoroborate) or a tri((C₁-C₂₀)hydrocarbyl)ammoniumtetra((C₁-C₂₀)hydrocarbyl)borane (e.g., bis(octadecyl)methylammoniumtetrakis(pentafluorophenyl)borane). As used herein, the term “ammonium”means a nitrogen cation that is a ((C₁-C₂₀)hydrocarbyl)₄N⁺, a((C₁-C₂₀)hydrocarbyl)₃N(H)⁺, a ((C₁-C₂₀)hydrocarbyl)₂N(H)₂ ⁺,(C₁-C₂₀)hydrocarbylN(H)₃ ⁺, or N(H)₄ ⁺, wherein each (C₁-C₂₀)hydrocarbylmay be the same or different.

Exemplary combinations of neutral Lewis acid activating co-catalystsinclude mixtures including a combination of a tri((C₁-C₄)alkyl)aluminumand a halogenated tri((C₆-C₁₈)aryl)boron compound, for example atris(pentafluorophenyl)borane.

Other exemplary embodiments are combinations of such neutral Lewis acidmixtures with a polymeric or oligomeric alumoxane, and combinations of asingle neutral Lewis acid, for example tris(pentafluorophenyl)boranewith a polymeric or oligomeric alumoxane. Exemplary embodiments ratiosof numbers of moles of (metal-ligandcomplex):(tris(pentafluorophenylborane):(alumoxane) [e.g., (Group 4metal-ligand complex):(tris(pentafluorophenylborane):(alumoxane)] arefrom 1:1:1 to 1:10:30, other exemplary embodiments are from 1:1:1.5 to1:5:10.

Many activating co-catalysts and activating techniques have beenpreviously taught with respect to different metal-ligand complexes inthe following patents: U.S. Pat. Nos. 5,064,802 and 5,198,401.

In some embodiments, the catalyst may be activated to form an activecatalyst composition by combination with one or more cocatalyst such asa cation forming cocatalyst, a strong Lewis acid, or a combinationthereof suitable cocatalysts for use include polymeric or oligomericaluminoxanes, for example methyl aluminoxane, as well as inert,compatible, noncoordinating, ion forming compounds. Exemplary suitablecocatalysts include, but are not limited to modified methyl aluminoxane(MMAO), bis(hydrogenated tallow alkyl)methyl,tetrakis(pentafluorophenyl)borate(1-) amine, triethyl aluminum, and anycombinations thereof.

In some embodiments, one or more of the foregoing activatingco-catalysts are used in combination with each other. One combination isa mixture of a tri((C₁-C₄)hydrocarbyl)aluminum,tri((C₁-C₄)hydrocarbyl)borane, or an ammonium borate with an oligomericor polymeric alumoxane compound.

In some embodiments, the ratio of total number of moles of one or moremetal-ligand complexes of formula (I) to total number of moles of one ormore of the activating co-catalysts is from 1:10,000 to 1:100. In someembodiments, the ratio is at least 1:5000, in some other embodiments, atleast 1:1000; and 1:10 or less, and in some other embodiments, 1:1 orless. When an alumoxane alone is used as the activating co-catalyst, inone embodiment, the number of moles of the alumoxane that are employedis at least 100 times the number of moles of the metal-ligand complex offormula (I). When tris(pentafluorophenyl)borane alone is used as theactivating co-catalyst, in some other embodiments, the number of molesof the tris(pentafluorophenyl)borane that are employed to the totalnumber of moles of one or more metal-ligand complexes of formula (I)form 0.5:1 to 10:1, in some other embodiments, from 1:1 to 6:1, in someother embodiments, from 1:1 to 5:1. The remaining activatingco-catalysts are generally employed in approximately mole quantitiesequal to the total mole quantities of the catalyst.

In an embodiment, the activator includes a boron ionic activator and analumoxane.

In an embodiment, the activator includes a boron ionic activator and analumoxane wherein the mole ratio of boron contained in said boron ionicactivator to the hafnium contained in said catalyst is from 1:1 to 2:1and the mole ratio of aluminum contained in said alumoxane to thehafnium contained in said catalyst is from 5:1 to 1000:1.

Solvent

A variety of solvents may be used as the process solvent; non-limitingexamples include linear, branched or cyclic C5 to C12 alkanes. It iswell known to individuals of ordinary experience in the art that reactorfeed streams (solvent, monomers, α-olefin, hydrogen, catalystformulation etc.) should be essentially free of catalyst deactivatingpoisons; non-limiting examples of poisons include trace amounts ofoxygenates such as water, fatty acids, alcohols, ketones and aldehydes.Such poisons are removed from reactor feed streams using standardpurification practices; non-limiting examples include molecular sievebeds, alumina beds and oxygen removal catalysts for the purification ofsolvents, ethylene.

Additives

The copolymers according to this disclosure may contain additives.

Non-limiting examples of additives and adjuvants include, anti-blockingagents, antioxidants, heat stabilizers, slip agents, processing aids,anti-static additives, colorants, dyes, filler materials, lightstabilizers, light absorbers, lubricants, pigments, plasticizers, andcombinations thereof.

Solution Polymerization Process and Comonomers

Solution polymerization processes are known in the art. These processesare conducted in the presence of an inert hydrocarbon solvent forexample a C₅₋₁₂ hydrocarbon which may be unsubstituted or substituted byC₁₋₄ alkyl group, such as pentane, hexane, heptane, octane, cyclohexane,methylcyclohexane and hydrogenated naphtha. An additional solvent isIsopar E (C₈₋₁₂ aliphatic solvent, Exxon Chemical Co.).

The polymerization may be conducted at temperatures from about 80° C. toabout 250° C. Depending on the product being made this temperature maybe relatively low such as from 80° C. to about 180° C. for some of theethylene propylene polymers and ethylene diene monomer polymers, totemperatures from about 120° C. to about 250° C. for the more conventionpolyethylenes, and copolymers of ethylene and styrene.

A solution polymerization may generally be conducted under pressures ofform 100 to 4500 psig (0.7 to 31 MPa). However, in some embodiments theprocess of this disclosure uses a pressure of at least 10.3 MPa.

Suitable olefin comonomers may be ethylene and C₃₋₂₀ mono- anddi-olefins. Example comonomers include ethylene and C₃₋₁₂ alpha olefinswhich are unsubstituted or substituted by up to two C₁₋₆ alkyl radicals,C₈₋₁₂ vinyl aromatic monomers which are unsubstituted or substituted byup to two substituents chosen from C₁₋₄ alkyl radicals, C₄₋₁₂ straightchained or cyclic diolefins which are unsubstituted or substituted by aC₁₋₄ alkyl radical. Illustrative non-limiting examples of suchalpha-olefins are one or more of propylene, 1-butene, 1-pentene,1-hexene, 1-octene, and 1-decene, styrene, alpha methyl styrene,p-t-butyl styrene, and the constrained-ring cyclic olefins such ascyclobutene, cyclopentene, dicyclopentadiene norbornene,alkyl-substituted norbornes, alkenyl-substituted norbornes and the like(e.g. 5-methylene-2-norbornene and 5-ethylidene-2-norbornene,bicyclo-(2,2,1)-hepta-2,5-diene).

In some embodiments, the polyethylene polymers which may be prepared inaccordance with the present disclosure may include not less than 60, forexample not less than 70 weight % of ethylene and the balance one ormore C₄₋₁₀ alpha olefins, for example chosen from 1-butene, 1-hexene and1-octene. The polyethylene prepared in accordance with the presentdisclosure may be linear low density polyethylene having a density fromabout 0.910 to 0.935 g/cc or (linear) high density polyethylene having adensity above 0.935 g/cc. The present disclosure might also be useful toprepare polyethylene having a density below 0.910 g/cc—the so-calledvery low and ultra low density polyethylenes.

The present disclosure may also be used to prepare co- and ter-polymersof ethylene, propylene and optionally one or more diene monomers. Insome embodiments, such polymers will contain about 50 to about 75 weight% ethylene, for example about 50 to 60 weight % ethylene andcorrespondingly from 50 to 25 weight % of propylene. A portion of themonomers, for example the propylene monomer, may be replaced by aconjugated diolefin. The diolefin may be present in amounts up to 10weight % of the polymer, or for example, in amounts from about 3 to 5weight %. The resulting polymer may have a composition including from 40to 75 weight % of ethylene, from 50 to 15 weight % of propylene and upto 10 weight % of a diene monomer to provide 100 weight % of thepolymer. Preferred but not limiting examples of the dienes aredicyclopentadiene, 1,4-hexadiene, 5-methylene-2-norbornene,5-ethylidene-2-norbornene and 5-vinyl-2-norbornene. In some embodimentsdienes are 5-ethylidene-2-norbornene and 1,4-hexadiene.

Other olefin polymers which may be prepared in accordance with thepresent disclosure may be determined by one of ordinary skill in the artusing non-inventive testing.

In some embodiments, the polymers prepared in accordance with thepresent disclosure have a molecular weight (Mn) greater than about20,000 (for example between 25,000 and 125,000).

In a solution polymerization the monomers are dissolved/dispersed in thesolvent either prior to being fed to the reactor, or for gaseousmonomers the monomer may be fed to the reactor so that it will dissolvein the reaction mixture. Prior to mixing, the solvent and monomers aregenerally purified to remove polar moieties. The polar moieties, orcatalyst poisons include water, oxygen, metal impurities, etc. In someembodiments, steps are taken before provision of such into the reactionvessel, for example by chemical treatment or careful separationtechniques after or during the synthesis or preparation of the variouscomponents. The feedstock purification prior to introduction into thereaction solvent follows standard practices in the art, e.g. molecularsieves, alumina beds and oxygen removal catalysts are used for thepurification of ethylene, alpha-olefin, and optional diene. The solventitself as well (e.g. hexane and toluene) is similarly treated. In someinstances, out of an abundance of caution excess scavenging activatorsmay be used in the polymerization process.

The feedstock may be heated prior to feeding to the reactor. However, inmany instances it is desired to remove heat from the reactor so the feedstock may be at ambient temperature to help cool the reactor.

In some embodiments, the catalyst components may be premixed in thesolvent for the reaction or fed as separate streams to the reactor. Insome instances premixing is desirable to provide a reaction time for thecatalyst components prior to entering the reaction. Such an “in linemixing” technique is described in a number of patents in the name ofDuPont Canada Inc. For example, it is described in U.S. Pat. No.5,589,555 issued Dec. 31, 1996.

The reactor system may include one or more reactors. It is well known touse two such reactors, in series, each of which may be operated so as toachieve different polymer molecular weight characteristics. Theresidence time in the reactor system will depend on the design and thecapacity of the reactor and the flow rate of the solvent and monomer tothe reactor. On leaving the reactor system the solvent is removed andthe resulting polymer is recovered in a conventional manner.

The process of this disclosure enables from 70 to 95% of the ethylenethat is fed to a reactor to be converted (polymerized) in a residencetime (also known as Hold Up Time) of from 0.5 to 5 minutes. For clarity,this rate of conversion must be achieved in at least one reactor.However, if a second or more reactor is employed, it is not required (inall embodiments) to achieve this rate of reaction in all reactors.

EXAMPLES Part 1: Chemicals and Common Procedures Handlings

Ethylene was purchased from Praxair as polymer grade. The ethylene waspurified and dried by passing the gas through a series of purificationbeds including alumina, 13X molecular sieves, and a conventionaldeoxygenation bed.

Purchased 1-octene was dried by storing a 1-liter batch over molesieve3A.

Methanol was purchased as GR ACS grade from EMD Chemicals.

Xylene was purchased from Univar. It was purified and dried by passingthrough a deoxygenation catalyst, alumina, and 3A and 13X molecularsieve beds). Cylcohexane was purchased from Univar. It was purified anddried by passing through a deoxygenation catalyst, alumina beds, and 3Aand 13X molecular sieve beds.

13x molecular sieves were purchased from Grace Davison and stored ingeneral lab storage. Before being used as a drying agent, the molecularsieves were heated for 16 hours at 360° C. to activate them and werethen pumped into a glovebox at full dynamic vacuum for at least 3 hours.3A molsieves: Pellets were activated in the same manner.

Triphenylmethylcarbenium tetrakis(pentafluorophenyl)borate [“tritylborate” ] was purchased from Albemarle and used without furtherpurification.

Modified methylaluminoxane-7 (MMAO-7) was purchased as a 7 wt % solutionin ISOPAR™ E from Akzo Nobel Polymer Chemicals. It was contained in apyrosafe cylinder and used as received in a glovebox.

2,6-di-tert-butyl-4-ethylphenol (BHEB) was purchased as a 99% purecompound and used without further purification.

The catalyst was made using techniques generally known to those skilledin the art and also disclosed in U.S. Patent Application No. 20150337062(Demirors et al.; to Dow Global).

Part 2: Polymerization and Polymer Characterizations

All the polymerization experiments described below were conducted usinga continuous solution polymerization reactor. The process is continuousin all feed streams (solvent, monomers and catalyst) and in the removalof product. All feed streams were purified prior to the reactor bycontact with various absorption media to remove catalyst killingimpurities such as water, oxygen and polar materials as is known tothose skilled in the art. All components were stored and manipulatedunder an atmosphere of purified nitrogen.

All the examples below were conducted in a reactor of 71.5 cc internalvolume. In each experiment the volumetric feed to the reactor was keptconstant and as a consequence so was the reactor residence time.

The catalyst solutions were pumped to the reactor independently andthere was no pre-contact between the activator and the catalyst. Becauseof the low solubility of the catalysts, activators and MAO incyclohexane, solutions were prepared in toluene. The catalyst wasactivated in situ (in the polymerization reactor) at the reactiontemperature in the presence of the monomers. The polymerizations werecarried out in cyclohexane at a pressure of 10.3 MPa. Ethylene wassupplied to the reactor by a calibrated thermal mass flow meter and wasdissolved in the reaction solvent prior to the polymerization reactor.If comonomer was used it was also premixed with the ethylene beforeentering the polymerization reactor. Under these conditions the ethyleneconversion is a dependent variable controlled by the catalystconcentration, reaction temperature and catalyst activity.

The internal reactor temperature is monitored by a thermocouple in thepolymerization medium and can be controlled at the set point to +/−0.5°C. Downstream of the reactor the pressure was reduced from the reactionpressure 10.3 MPa to atmospheric pressure. The solid polymer was thenrecovered as a slurry in the condensed solvent and was dried in vacuumoven before analysis.

The ethylene conversion was determined by a dedicated on-line gaschromatograph. The average polymerization rate constant Kp wascalculated based on the reactor hold-up time, the catalyst concentrationand the ethylene conversion and is expressed in l/(mmol*min).

Kp is calculated as Kp=(Q/(100−Q))1×(1/TM)×(1/HUT)

where:

-   -   Q=the percent ethylene conversion    -   TM=the reactor catalyst concentration in mM    -   HUT=the reactor hold-up time in minutes

Polymerization results are shown in Table 1.

Polymer Analysis

GPC analysis was carried out using a Waters 150 C GPC using1,2,4-trichlorobenzene as the mobile phase at 140° C. The samples wereprepared by dissolving the polymer in the mobile phase solvent in anexternal oven at 0.1% (w/v) and were run without filtration. Molecularweights are expressed as polyethylene equivalents with a relativestandard deviation of 2.9% and 5.0% for the number average (Mn) andweight average (Mw) respectively. Poly dispersity (“PD”) is Mw/Mn.

Polymer densities were measured using pressed plaques (ASTM D-1928-90)with a densitometer.

Polymer branch frequencies (SBr) and polymer unsaturation weredetermined by Fourier Transform Infra Red (FT-IR) spectroscopy. Theinstrument used was a Nicolet 750 Magna-IR spectrophotometer.

Unsaturation data are shown in Table 2. The data in Table 2 illustratethat, under the polymerization conditions of these examples, the levelof unsaturation may be controlled (increased) by increasing thepolymerization temperature. (The run numbers in Table 2 correspond tothose of Table 1.)

TABLE 1 Catalyst Activity and Polymer Molecular Weight Under VaryingProcess Conditions Reactor Run Temp. C2 C8/C2 Kp Mw SBr/ Catalyst # (°C.) g/l (wt/wt) Q (%) (1/mM*min) (10⁻³) PD 1000C uM Al/Hf 1 220 160 0.389.62 677 132.4 2.3 14.6 4.9 4.1 2 220 180 0.3 89.66 463 123.0 2.0 14.97.2 2.8 3 190 130 0.3 90.20 1826 203.3 2.1 15.4 1.9 10.3 4 190 180 0.390.52 620 154.1 2.2 13.9 5.9 3.4 5 160 100 0.3 90.58 10682 326.6 2.316.7 0.35 57.8 6 160 100 0.3 90.28 6449 297.1 2.3 17.1 0.56 36.1 7 160100 0.5 89.57 5962 295.4 2.3 27.8 0.56 53.9 8 160 100 0.7 89.45 5887263.6 2.3 35.8 0.56 36.1 C2 = ethylene C8 = octene

The total flow of solvent and ethylene was 27.5 ml per minute whichprovides hold up times (HUT) of between 2.1 minutes (for the ethyleneflow rate of 75 grams of ethylene per liter of feed) and 1.9 minutes(for the ethylene flow rate of 120 grams of ethylene per liter of feed).

The catalyst used in all examples is described by the following formula:

The catalyst was activated with methylalumoxane (MAO) and trityl borate.The reactor catalyst concentration (expressed as uM of Hf) is shown inTable 1, as is the Al/Hf mole ratio. Trityl borate was used in a B:Hfmole ratio of 1:2/1 in all experiments. BHEB was also used at a moleratio (BHEB:Al) of 0.3:1 in all experiments.

TABLE 2 Unsaturation Levels Reactor Temperature Unsaturation Run# (° C.)(Vinyls per 1000 Carbon Atoms) 2 220 0.22 4 190 0.19 6 160 0.1 8 1600.09

INDUSTRIAL APPLICABILITY

The copolymerization of ethylene and comonomer(s) is disclosed. Theresulting polymers are suitable for the preparation of a wide variety ofgoods including plastic toys; plastic parts and profiles and plasticfilms.

1. A process for the (co)polymerization of ethylene and, optionally, atleast one C₃ to C₁₀ alpha olefin comonomer wherein said process isconducted under solution polymerization conditions using a catalystsystem comprising: A) a catalyst defined by the formula:

M is titanium, zirconium, or hafnium, each independently being in aformal oxidation state of +4; n is 2; Each X independently is amonodentate ligand; X is chosen in such a way that the metal-ligandcomplex of formula (I) is, overall, neutral; L is hydrocarbylene orheterohydrocarbylene, wherein the hydrocarbylene has a portion thatcomprises a 1-carbon atom to 6-carbon atom linker backbone linking the Oatoms in formula (I) and the heterohydrocarbylene has a portion thatcomprises a 1-atom to 6-atom linker backbone linking the O atoms informula (I), wherein each atom of the 1-atom to 6-atom linker backboneof the heterohydrocarbylene independently is a carbon atom or aheteroatom, wherein each heteroatom independently is O, S, S(O), S(O)₂,Si(R^(C))₂, Ge(R^(C))₂, P(R^(P)), or N(R^(N)), wherein independentlyeach R^(C) is unsubstituted (C1-C18)hydrocarbyl or the two R^(C) aretaken together to form a (C2-C19)alkylene, each R^(P) is unsubstituted(C1-C18)hydrocarbyl; and each R^(N) is unsubstituted(C1-C18)hydrocarbyl, a hydrogen atom or absent; Each of R^(1a), R^(1b),R^(2a), R^(2b), R^(3a), R^(3b), R^(4a), R^(4b), R^(5c), R^(5d), R^(6c),R^(6d), R^(7c), R^(7d), R^(8e), R^(8f), R^(9e), R^(9f), R^(10e),R^(10f), R^(11e), R^(11f), R^(12e), R^(12f), R^(13e), R^(13f), R^(14e),R^(14f), R^(15e), R^(15f) independently is a hydrogen atom; hydrocarbyl;heterohydrocarbyl; or halogen atom; B) and an activator, wherein saidsolution polymerization is conducted under the following conditions: 1)an ethylene feed concentration of from 70 to 200 grams per liter of feedsolvent; 2) a pressure of from 10.3 to 31 MPa; 3) a reactor residencetime of from 0.5 to 5 minutes, with the proviso that from 50 to 95weight % of the ethylene in said feed is converted to polymer withinsaid residence time of from 0.5 to 5 minutes, with the proviso that thepolymerization is conducted at a temperature of greater than 160° C. soas to produce an ethylene polymer having a degree of unsaturation ofgreater than 0.1 vinyl groups per 1000 carbon atoms as measured byFourier Transform Infra Red spectroscopy.
 2. The process of claim 1wherein said L is hydrocarbylene and comprises a 1-carbon atom to6-carbon atom linker.
 3. The process of claim 1 wherein said at leastone C₃ to C₁₀ comonomer is chosen from propylene; 1-butene; 1-hexene and1-octene.
 4. The process of claim 1 wherein said activator comprises aboron ionic activator.
 5. The process of claim 1 wherein said activatorcomprises a boron ionic activator and an alumoxane.
 6. The process ofclaim 1 wherein said M is hafnium.
 7. The process of claim 6 whereinsaid activator comprises a boron ionic activator and an alumoxane. 8.The process of claim 7 wherein the mole ratio of boron in said boronionic activator to the hafnium in said catalyst is from 1:1 to 2:1 andthe mole ratio of aluminum in said alumoxane to the hafnium in saidcatalyst is from 2:1 to 1000:1.